The invention relates to potentiometers and the wipers used therein to make a sliding contact with an electrically conductive element.
Wipers used with conductive plastic resistance elements have conventionally followed a design developed for wipers used with the older, wire-wound resistor elements. Such wipers, used in position transducers, have been simply shaped elements made from metals chosen with regard to their static properties such as spring constant, electrical conductivity, corrosion resistance and wear resistance. Potentiometers are, in fact, transducers, i.e., devices that yield an electrical output for a given mechanical input, and the applications for such transducers are increasing. Potentiometers designed and manufactured using conventional wiper designs have serious inadequacies when used in high precision, high speed applications. In particular, the potentiometers displayed hysteresis in that the relationship between electrical and mechanical settings depends on the direction of most recent motion of the wiper, and this effect limited the precision of the potentiometer, especially with oscillating movement. Additionally, when the velocities and accelerations of wiper motion became large, there was intermittent interruption of the electrical contact between the wiper and the resistance element. The lifetime of such potentiometers used in automatic control circuits, especially where they are subject to frequent oscillating movement, has not been satisfactory because of high wear and wiper fatigue breakage in such service.